Observation of a screw dislocation in the Hg-1223 superconductor under a transmission electron microscope

Screw dislocations were observed in a Hg-1223 sample under the transmission electron microscope. A typical dislocation reported here, was observed on the (110) plane of the Hg-1223 unit cell. The angle between the Burger's vector and the [001] crystal direction of the Hg-1223 unit cell is 26°, and the magnitude of the Burger's vector is 17.63 angstroms. 2D and 3D diagrams showing this dislocation are presented in order to explain its configuration. A simple semi-quantitative model is also proposed to describe the occurrence of the screw dislocation based on an analysis of the shear stress along the (110) plane. It is believed that the formation of this screw dislocation is due to the intergrowth of different Hg superconducting phases during the special solid state reaction of the Hg superconductor. These intergrowth structures generate a stress field inside the lattice of the Hg sample, which indicates various kinds of microdefects such as the screw dislocation.